Chronic, complete cervical6‐7 cord injury: distinct autonomic, cardiac and vascular deficits

Abstract

Spinal cord injury (SCI) resulting in tetraplegia is a devastating, life‐changing injury causing paralysis and sensory impairment as well as autonomic dysfunction that triggers compromised cardiovascular, bowel, bladder and sexual activity. Life becomes a battle for independence as even routine bodily functions and the smallest activity of daily living become a major challenge. The human physiology, mind and spirit are wonderfully adaptable as individuals with tetraplegia find ways to adjust. However, addressing autonomic losses and cardiovascular consequences would greatly improve the quality of life for individuals living with tetraplegia. Virtually all pre‐clinical investigations of autonomic losses and cardiovascular consequences following SCI induce lesions in the thoracic region. However, cervical lesions produce distinct autonomic, cardiac and vascular deficits and result in the most dramatic autonomic outcomes and cardiovascular consequences. Specifically, although cardiovascular disease (CVD) is the leading cause of morbidity and mortality for individuals living with SCI, the magnitude of CVD risk is dependent on the level of SCI, whereby individuals with tetraplegia have a 16% greater risk of all‐cause CVD than individuals with paraplegia. Accordingly, there is a critical need for a chronic pre‐clinical model of tetraplegia. In this report, we compare resting cardiac sympathetic and parasympathetic tonus, reflex sympathetic effects (heart rate responses to sodium nitroprusside), tonic autonomic effects (responses to autonomic ganglionic blockade), cardiac responses to beta‐adrenergic stimulation and the response to angiotensin‐converting enzyme inhibition in 6 rats with chronic (4 week) complete C6‐7 transection and 6 intact sham‐transected rats. Histological examination of the heart and stellate ganglia support the profound and distinct autonomic and cardiac deficits and reliance on angiotensin to maintain cardiovascular stability following chronic, complete cervical6‐7 cord transection.Support or Funding InformationR01HL122223